Method for distilling heavy oils



G. B; COUBROUGH METHOD FOR DISTILLING HEAVY OILS Filed Jan. 21, 1930Patented May 30, 1933 UNITED STATES PATENT OFFICE- GEOBGE B. COUIBROUGH,OF LONG BEACH, CALIFORNIA ASSIGNOR BY MESNE ASSIGN- 1 MENTS TO THELUMM'U S COMPANY, A CORPORATION OF DELAWARE METHOD FOR DISTILLIN'G HEAVYOILS Application filed January 21, 1930. Serial No. 422,344.

The present invention relates to methods and apparatus for distillingheavy oils.

The recovery of heavy oils such as wax distillates from petroleumbottoms is usually attended with difficulties, principally due to thehigh temperatures which must be employed for distillation and which tendto cause decomposition or cracking. Batch methods of distillation areobjectionable in that the temperature increases as vaporizationproceeds. Flash vaporization, as practised under existing methods, isnot entirely satisfactory because the entire heat of vaporization of thedistillate oils is taken from heat stored in the residual oil so thatupon vaporization of the desired components, the temperature falls to apoint below which vaporization cannot continue. In either case,vaporization of the valuable constituents comes to an end before theavailable quantity of product is obtained.

.The object of the present invention is to provide a method andapparatus for distilling heavy oils from bottoms to obtain the a maximumrecovery of the valuable constituents and at temperatures notsufliciently high to effect undesirable decomposition,

With this object in view, the present invention makes use of the methodwhich consists in first heating the bottoms from which it is desired torecover one of more oils as a product and introducing the heated bottomsinto a column where vaporization is facilitated by vacuum, or by acounter-current of steam. It has always been consid- 1 ered that themost favorable composition of the original mixture for large recovery ofdistillate comprises a large percentage of the lighter desired oils andonly a small percentage of residual product, for the reason that theboiling point of the mixture is not greatly higher than the boilingpoint of the overhead product alone. I have discovered, however, thatthe conditions which have heretofore been considered most favorable arein fact thev least conducive to complete recovery of the distillate oilsand that for maximum effectiveness of distillation, the original mixtureshould contain only a small proportion of the oils desired as distillateand a relatively lar e proportion of materials ;having a su stantiallylower vapor pressure. When the bottoms which are to be divided contain arelatively small percentage of lighter oils desired as distillate inaccordance with the present invention, the remaining relativelyunvaporizable components act as a large heat reservoir to maintain thetemperature of the mixture against excessive depression upon abstractionof the heat required to vaporize the entire body of distillate oils. Animportant feature of the invention, therefore, comprises adding to theoriginal bottoms a quantity of relatively unvaporizable heat holdingmaterial prior to heating of the mixture and introduction thereof intothe vaporizer column, the quantity of heat holding material added beingsuflicient to maintain the temperature against depression below theboiling point upon vaporization of the lighter oils.

This important feature of the present invention is of particular valuein recovering heavy lubricating stock (heavy wax distillate) frombottoms whichcomprise a mixture of the lubricatin The asphalt, althougitself a non-volatile substance, tends to hold the lubricating stockinsuch stable equilibrium therewith that recovery of all of thelubricating stock including the heaviest and most valuable endcomponents is by ordinary methods extremely diflicult. According to thepresent invention, such bottoms prior to heating are mixed with asuflicient quantity of heat holding material to make the lubricatingstock only a small proportion of the total mixture. Preferably the heatholding material is additional asphalt which forms a stock with asphalt.

part of the residual product and which does "mixture therewith.

The invention although described above as being applicable to therecovery of heavy lubricating stock from an asphaltic residue is notlimitd in its use to such products but may be employed for separatingoils from each other whether or not asphalt may be present. Thus theprocess may be employed for distilling oif a light wax distillate,leaving a residue of heavy lubri+ Thus in the case of separation ofheavy wax distillate from asphalt, a predetermined percentage of theaszphaltic residue is pumped back to be mixed directly with the bottomspassing to the heater. This feature of the invention efl'ectssubstantial economies in operation in that the sensible heat of theresidue is available for heating 'the original mixture.

The vaporization step may be carried'out underd vacuum or with steam. Ind vacuum istillation, the addition of the heat holding material acts toraise the boiling point of the mixture, the rise in boiling point,however, being more than ofiset by the maintenance of temperatureafforded by the increased capacit for storing heat. But the use of steamo ers the additional advantage that the boiling point of the mixture isnot greatly increased by the addition of the heat storing material, andtherefore the maximum advantage of the augmented heat storage capacityis obtained. In distilling extremely heavy oils, the use of a vacuumtogether with steam is to be preferred because the advantages of both,temperature methods are availed of, and the oils are well protectedagainst decomposition.

Other features of the invention consist of certain novel features ofconstruction and modes of operation hereinafter described andparticularly defined in the claims.

In the accompanying drawing, Fig. 1 is a diagrammatic illustration ofthe preferred form of apparatus for practising the invention to distillheavy oils with steam and Fig. 2 is a diagram of the preferred form ofapparatus for practising the invention under dry vacuum.

The invention is herein illustrated and described as embodied in amethod and appa ratus for recovering heavy lubricatin stock (heavy oramorphous wax distillate from bottoms which comprise a mixture of thelubricating stock with asphalt.

Referring to Fig. 1 which shows an apparatus for practising theinvention with steam, the bottoms are pumped through 9.

supply line 4 by a pump 6 to a heater 8 where they are heated to themaximum safe temperature without decomposition. The heated oil isadmitted into a mediate oint of a vaporizin column 10 into whic thesteam is intro need through a perforated steam pi e 12 at the bottom.The heated mixture ows downwardly over boiling ca decks 14 where it issubjected to the ascen ing steam. In this zone, the lubricating stock isremoved from the asphalt, the latter being collected in the bottom ofthe column and drawn off by a pipe 16. The pipe 16 connects by a pipe 18with the inletside of the pump 6 so that a part of the asphalt isrecirculated through the pump and heater to be again introduced into thecolumn. The remainder of the asphalt is drawn oil as a product throughthe pipe 20, theamount of recirculated asphalt being controlled by avalve 22 in the ofi'take pipe.

Above the point of admission of the oil into the column, there areprovided a series of entrainment catching decks 24 to remove particlesof asphalt which may be carried upwardly by the ascending current ofsteam and vapor. The mixture of steam and vapor continues through acenter pipe 26 which extends upwardly from a collecting deck 28.Inasmuch as it is undesirable to condense the steam-vapor mixturebecause of the tendency to form emulsions with the wax, the waxdistillate is liquefied in the upper section 30 of the column by meansof a counter-current of a light non-emulsifiable oil introduced into thetop of the column. The non-emulsifiable oil preferably comprises gas oilwhich is contained in a supply tank 32 and admitted to the columnthrough a pipe 34.' A plurality of boiling cap decks 36 are provided inthe upper part of the tower. As described in the co-pending applicationof Coubrough, Serial No. 355,871 filed April 17, 1929, the gas oildisplaces the heavy wax distillate from the ascending steam-vapormixture ermitting the wax distillate to collect on t e deck 28 fromwhich it is drawn off through a pipe 38 controlled bya valve 40. Themixture of steam and gas oil passes out of the column through a vaporpipe 42 to be condensed in a condenser 44. The condenser discharges intoa bottle 46 from which the Water and gas oil are drawn off through pipes48 and 50. If a vacuum is to be employed in combination with the steam,the bottle connects with a vacuum line 52 leading to a suitable vacuumpump. Even with the heaviest oils, the vacuum need not be -too high torender the use of boiling cap of asphalt may be adjusted to make theasphalt comprise as much as of the entering mixture. The proportions,having been once established, may be easily maintained by properregulation of the rate of withdrawal of the asphaltic residue throughthe pipe 20.

The bottoms are heated in the heater to the maximum safe temperaturewithout decomposition and a suflicient quantity of steam is employed toinsure complete vaporization of the lubricating stock. By the presentinvention, substantially all of the wax distillate is vaporized in asingle passage through the counter-current zone 14, the recirculatedasphalt containing practically none of the valuable oil constituents.The seplaration has been found to be so complete t at care must be takento maintain the asphalt in the pipes 18 and 20 at a temperature abovethe melting point, otherwise an actual solidification of pure asphaltmay occur. The recovery of the residue as an asphaltic product capableof solidification upon cooling is indicative of the complete removal ofthe valuable oil constituents.

The recirculation of the residue comprises in effect the addition ofheat storing material to the bottoms. Upon admission of the mixture intothe column, vaporization of the oils takes place, owing to the contactof the heated liquid with the steam, and because of the reduction inpressure if a vacuum is employed. Inasmuch as the only heat availablefor the latent heat of vaporization of the distillate components is thesensible heat of the mixture, a drop in temperature immediately follows.It is to be noted that the steam is not employed to contribute heat tothe mixture; its purpose is to facilitate vaporization of the volatileoils, and it may in fact be itself heated by the mixture as it risesthrough the vaporizing zone.

It will be seen that according to ordinary methods of heavy oilrecovery, the temperature drops rapidly until it reaches a point nolonger effective to vaporize the distillate components. According to thepresent invention, however, the presence of a large heat reservoir ofsubstantially less volatile material than the distillate maintains thetemperature against depression below the boiling point of the mixtureuntil complete vaporization of the distillate has been effected.

The invention as above described is employed for the recover of a heavythough volatile oil product i i'om a substantially non-volatile residue.The invention may also be employed to efi'ect a separation between twovolatile products, for example, to efiect a sharp out between a lightlubricating stock to be obtained as a distillate and a heavy lubricatingstock to fall into the residue. In order to prevent depression of thetemperature upon vaporization ofthe lighter oils, the residue isrecirculated through the pipe 18. This process is useful both on oilswhich contain asphalt. and those which have no asphaltic content.

In Fig. 2 is shown an apparatus for practising the present inventionunder dry vacuum. The supply line 4, the pump 6, the.

heater '8, the residue draw-off pipe 16 and the recirculating pipe 18are as in Fig. 1. The oil heated in the heater 8 is admitted to thevacuum column 60 at a mediate point and the oil flows downwardly overdecks 62 which are preferably of the staggered or overlapping type inorder not to seal against the high vacuum. The upper part of the columnis provided with entrainment catching decks 64. The vapors pass'into acondenser 66 from which the condensate is discharged into a bottle 68connected with a vacuum line 70. The distillate is drawn ofi' directlyby a pipe 72. l

The method of distillation under dry vacuum is similar to the steamdistillation method described above in that the addition to the bottomsof a material having a high heat storage capacity makes for main tenanceof temperature in the column even though substantially completevaporization of the distillate is carried out.

Although the specific embodiments of the invention are described asrelying on the recirculation of the residual product for creating theheat storage reservoir for the mixture, it will be understood that it isnot essential to employ the residual material of the process for thispurpose although such operation is desirable because of the economy ofoperation. The heat storage material may be added to the original supplyand later recovered from the residue. The use of asphalt as a heatstorage medium is to be preferred because of its extremely low volatility, whereby in the specific example given above of recoveringheavy wax distillate from'the asphalt, no problem of fractionation orrectification is presented.

Having thus described the invention, what is claimed is:

1. A method of recovering oils from petroleum bottoms containing asphaltwhich consists in adding to the original bottoms a quantity of asphalthaving high heat stor-' age capacity, heating the mixture, continuouslyadmitting the heated mixture into a vaporizing zone in counter-currentwith steam to vaporize the oils by the heat stored. in the mixture, thequantity of added asphalt being suflicient to maintain the temperatureagainst depression to a point below which vaporization cannot continue,until substantially complete vaporization of the oils has been efiected.

2. A method of separating heavy oils I from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heating the mixture, and admitting the heatedmixture into a vaporizing zone in counter-current with steam, thequantity of asphalt added being sufficient to supply the heat ofvaporization of the oils without excessive depression of temperature.

3. A method of recovering oils from petroleum bottoms containing asphaltwhich consists in adding to the original bottoms a quantity of asphalthaving high heat stor age capacity, heating the mixture, continuouslyadmitting the heated mixture into a vaporizing zone maintained undervacuum to vaporize the oils by the heat stored in the mixture, thequantity of added asphalt being suflicient to maintain the temperatureagainst depression to a point below which vaporization cannot continue,until substantially complete vaporization of the oils has beenefl'ected.

4. A method of separating heavy oils from bottoms containing asphaltwhich consists adding to the bottoms a quantity of asphalt to act as aheat storage medium, heatmg the mixture, and admitting the heatedmixture into a vaporizing zone maintained under vacuum, the quantity ofasphalt added being sufiicient to supply the heat of vaporization of theoils without excessive depression of temperature.

5. A method of separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heatmg the mixture, admittingthe heated mix tureinto a vaporizing zone maintained under vacuum, the quantity of asphaltadded being sufficient to supply the heat of vaporization of the oilswit sion of temperature, withdrawing asphalt from the vaporizing zone,and recirculating a part of the asphalt withdrawn to serve as the heatstorage medium to be mixed with the original bottoms.

6. A method of separating heavy oils from bottoms containing asphaltwhich consists in adding to the bottoms a quantity of asphalt to act asa heat storage medium, heating the mixture, admitting the heated mixtureinto a vaporizing zone in countercurrent with steam, the quantity ofasphalt added being suflicient to supply the heat of vaporization of theoils without excessive depression of temperature, withdrawing asphaltfrom the vaporizing zone, and recirculating a part of the asphaltwithdrawn to serve as the heat storage medium to be mixed with theoriginal bottoms.

In testimony whereof I have signed my name to this specification.

GEORGE B. 'COUBROUGH.

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